1. Field of the Invention
The present invention relates to apparatus for evaluating a scanning locus and, more particularly, to such apparatus suitable for use in evaluating the scanning locus traced by rotary heads with respect to recording tracks obliquely formed on a tape.
2. Description of the Prior Art
Conventionally, in a rotary head type digital audio tape recorder (a so-called R-DAT), a magnetic tape used as a recording medium is obliquely lapped around a rotary drum having rotary magnetic heads mounted thereon. The tape is caused to travel in a direction K1, as FIG. 1 shows. While the magnetic tape travels in the direction K1, the rotary magnetic heads scan the magnetic tape 1 in a head scanning direction K2 that forms an acute angle with the direction K1. The rotary magnetic heads obliquely traverse the magnetic tape 1, whereby oblique recording tracks 3 are formed on the tape successively connected to one another in the tape traveling direction K1.
In a rotary head type recording and reproducing apparatus of the type described above, there is a possibility of a malfunction occurring in recording and reproducing an information signal on the recording tracks 3 if the drive system causing the magnetic tape 1 to travel around the magnetic drum, i.e., the tape path system, does not work correctly. Therefore, it becomes necessary to evaluate the tape path system to determine whether it is "good" or "bad." This can be done, for example, during the process of fabricating the rotary head type recording and reproducing apparatus by closely inspecting the operating conditions of the tape path system, such as the contacting condition of the rotary magnetic head with respect to the tape, the contacting width of the rotary magnetic head, possible meandering of the recording tracks, etc.
In a conventional method for evaluating the tape path system, a signal is recorded in recording tracks 3 formed on a tape 1 in a recording mode, and the recorded signal is picked up in a reproducing mode from the recording tracks 3. The envelope waveform of the picked-up signal is displayed on the screen of an oscilloscope, and the envelope is visually examined by an inspector to determine the existence of any abnormalities.
More specifically, in the case where the rotary head type recording and reproducing apparatus to be inspected is of a tracking control type, i.e., a type in which the rotary magnetic head is tracking-controlled to follow the recording track 3 in the reproducing mode, the scanning locus HED of the rotary magnetic head is traced on the recording track 3 as shown in FIG. 1, whereby an envelope waveform ENV1 continuously held virtually at a constant level during a scanning period T.sub.SCN of the rotary magnetic head is normally displayed on the screen of the oscilloscope as shown by ENV1 in FIG. 2. If an abrupt change in the envelope waveform ENV1 is found, as indicated at WX1, the tape path system is evaluated to be faulty at a scanning position corresponding to the location of the abrupt change.
On the other hand, if the rotary head type recording and reproducing apparatus is of a type in which the rotary magnetic head, in the reproducing mode, is not tracking-controlled to follow the recording track 3 (which system is called a non-tracking system), and if the scanning angle of the rotary magnetic head with respect to the recording track 3 deviates from that in the recording mode, the scanning locus HED of the rotary magnetic head intersects the recording tracks 3 as shown in FIG. 3A or FIG. 3B. As a result, an envelope waveform as shown by ENV2 in FIG. 2, the so-called "barreled" envelope waveform ENV2, in which the level of the envelope waveform diminishes when the scanning locus HED shifts from one recording track 3 to the next recording track 3, is displayed.
In practice, it is often difficult to tell by observation of an oscilloscope whether or not there is a defect in the envelope waveform and whether or not the scanning angle of the rotary magnetic head is proper with respect to the recording track 3.